Textbooks are getting more and more expensive, and students are increasingly resistant to buying them. We see more and more students in the library hoping that we have their textbook on our shelves (we usually don't, and if we did someone else has already borrowed it). By using an Open Textbook or other basing your course around other freely available resources (such as other OERs and materials available through the library and/or put on reserve) you can save your students a lot of money.
For more information we suggest exploring visiting the Open Textbook page, which has links to what other universities and colleges are currently working on. There you will find a list of Alternate Textbook projects, put together by Temple University Library as well as links to the Open Textbook project, from BCcampus.